bug#48500: 28.0.50; url-retrieve-synchronously exits abnormally due to pending keyboard input from terminal

[Shane Mulligan <mullikine@gmail.com>]

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My apologies. It was literally 5am when I wrote that. I think I have
misunderstood `C-g` being generated with `quit-flag`. The bad behaviour is
very clearly still happening. I will try to clarify this problem further by
experimenting with it. I need to figure out why `while-no-input` suppresses
the `quit` but merely setting `quit-flag` does not. Something indirect may
be happening.

Thank you all,
Shane Mulligan

How to contact me:
🇦🇺 00 61 421 641 250
🇳🇿 00 64 21 1462 759 <+64-21-1462-759>
mullikine@gmail.com


On Wed, May 19, 2021 at 4:54 AM Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Shane Mulligan <mullikine@gmail.com>
> > Date: Wed, 19 May 2021 04:32:16 +1200
> >
> > Thanks for looking into this so quickly. First some background on the
> problem. I managed to work through
> > this issue (https://github.com/emacs-helm/helm/issues/2417) with the
> `emacs-helm` maintainer and we
> > found what appears to be that the call to `accept-process-output` inside
> of `url-retrieve-synchronously` will
> > generate a `C-g` when there is pending input of any char. As far as I
> can tell this is an issue only with
> > terminal emacs. As I understand it, `inhibit-quit`, as used in
> `accept-process-output` allows a `C-g` to be
> > propagated outwards and handled and from what I can see by the comments
> surrounding,
> >
> > ```
> >               ;; accept-process-output returned nil, maybe because the
> process
> >               ;; exited (and may have been replaced with another).  If
> we got
> >               ;; a quit, just stop.
> > ```
> >
> > the `C-g` in this case is expected.
> >
> > But I wonder if `C-g` was meant to be generated if the user was simply
> mashing keys on the keyboard.  In
> > this case, the `C-g` emanating from `accept-process-output` was bubbling
> up into `helm` and `helm` was
> > treating it like an error.
> >
> > Here, you can see a quit being generated from the visual cue in the
> minibuffer.
> > https://asciinema.org/a/nAIB8Z1lGgZJqJg9Mt8YiNEM9
> >
> > Here, I have added `while-no-input` and I no longer get the `quit`.
> > https://asciinema.org/a/x9ELZhwDP1IUtmOz0M1cly42H
> >
> > However, as I test the addition of `while-no-input` with
> `helm-google-suggest` (as above), though Quit is no
> > longer being generated from mashing keys, the key input which would have
> generated the `quit` is not
> > immediately shown in `helm`. Instead, it only appears on the next key
> press. So my implementation may not
> > be perfect or complete.
> >
> > Finding the solution would make the minibuffer far less interrupted
> while typing when
> > `url-retrieve-synchronously` is used in the background.
> >
> > Thank you.
> >
> > Shane Mulligan
>
> Please in the future send your responses with the bug address,
> 48500@debbugs.gnu.org, on the CC list, so that others will see your
> detailed descriptions.  I won't have time to take a good look into
> that in the next few days, so it's good to make others aware of your
> findings, because they might look into it meanwhile.
>
> Personally, I find it very strange that typing on the keyboard
> produces C-g, it shouldn't happen, neither on a TTY nor on a GUI
> display.
>

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